Psychologists in the Netherlands have documented the case of a 58-year-old woman who was misdiagnosed with Alzheimer's Disease. Her condition deteriorated to the point where she became permanently confused, and at one point suicidal — before another doctor realized the diagnosis was incorrect.

What happens to people who are wrongly diagnosed with having cognitive difficulties? It turns out that even if your brain is perfectly healthy, you'll start having more problems with concentration.

Top image: Wallenrock/Shutterstock.

So how did this 58-year-old woman come to be misdiagnosed with Alzheimer's? She consulted a neurologist at a stressful time in her life, in the knowledge that her mother had had the illness. A brain scan indicated reduced activity at the front of her brain ("hypofrontality"), and the neurologist also estimated her performance on a test of cognitive impairment as poor (though no formal test was conducted). On this basis he diagnosed Alzheimer's.

(Many years later, the neurologist was found guilty of having misdiagnosed several patients with Alzheimer's and 26 malpractice suits were filed against him, but the woman featured in this case study was not part of that litigation.)

The woman was devastated, and thereafter her condition deteriorated significantly, to the point that she was permanently confused and, at one point, suicidal. Some months later, after receiving advice from an Alzheimer's helpline, the woman consulted a different neurologist for a second opinion. She completed comprehensive memory tests and undertook a further brain scan. All results were normal. This neurologist surmised that her earlier hypofrontality was associated with depression. He also went to great lengths to explain the good news about her results and the misinterpretation of her earlier scan, but it proved extremely difficult to assuage her concerns.

Years later, Harald Merckelbach and his team have interviewed the woman and they report that she continues to experience intrusive thoughts about the misdiagnosis and to catastrophise her memory lapses. Merckelbach's group believe the effect of a misdiagnosis has parallels with the implantation of false memories. Just as false memories are difficult to reverse, so too are mistaken diagnoses. "Conferring a diagnostic label is far from a neutral act," they said. "Many diagnostic labels have strong stereotypical connotations and sometimes, these will automatically shape the experiences and behaviour of patients, a phenomenon called 'diagnoses threat'."

To test these ideas further, Merckelbach, with colleagues Marko Jelicic and Maarten Pieters, gave 78 undergrads a psychological symptoms questionnaire to complete. Afterwards the students performed Suduko puzzles as a distraction. Next, the researchers went through some of the students' answers with them. During this review, the researchers inflated two of the answers they'd given to anxiety items. For example, imagine a student had originally indicated that she never had trouble concentrating. The researcher would inflate that answer by two points on the scale, as if she'd said that she sometimes had trouble concentrating, and they then asked the student to explain why she'd given that answer.

Remarkably, 63 per cent of the participants failed to notice that their answers had been altered, and they proceeded to describe their experience of the symptoms (readers may notice parallels here with a phenomenon known as "choiceblindness", in which people seem to have little insight into a recent choice they made).

Ten minutes later, and again after one week, all the students re-took the psychological symptoms questionnaire. At both time points, students who'd earlier failed to notice that two of their answers had been altered, now gave higher ratings to those two items, as if they considered themselves to have those symptoms. Such an effect was not observed among the minority of students who'd earlier noticed that their answers had been altered. An analysis of all the students' original baseline answers uncovered higher average baseline symptoms among those who would fail to notice the inflation of their answers.

"Apparently a non-zero symptom intensity level introduces ambiguity; thereby raising the probability that misinformation is accepted," the researchers said. However, it's not the case that the influenced participants were simply more keen to give answers that the researchers wanted - they scored just the same on a test of social desirability.

Harald Merckelbach and his colleagues said their findings had particular significance for the way medical professionals interact with patients with unexplained symptoms, including those labelled with chronic fatigue, fibromyalgia, irritable bowel syndrome, and chronic pain. "... Expressing concern about the possibility of an underlying illness and, related to this, excessive investigation and attending patient support groups may all contribute to symptom escalation. What these interventions have in common is that they convey the message to the patient that his or her symptoms might be more intense and severe than he/she thinks they are. Our study suggests that blindness to unintended misinformation about the severity of the symptoms may underlie escalation of symptoms."